The forced swim test is a behavioral test that involves placing a rat or mouse in a cylinder with enough water so that it cannot touch the bottom with its hind paws. It is used to test the rats responsiveness to stress. A normal animal will show an immediate burst of activity, try to escape, and then eventually adopt an “immobile” posture, where it will make only those movements necessary to keep its head above water. 

Forced Swim Test

The elevated plus maze is used to evaluate anxiety-like behaviors in rodents. Subjects are placed in the junction of the maze, and their entries into either the open arms or the closed arms are recorded over a set duration. Unlike traditional methods of measuring anxiety in rodents, such as food deprivation or shocks, the elevated plus maze does not present a noxious stimuli and therefore does not lead to aversive conditioning. Wild-type rodents gravitate toward the dark, enclosed arms of the maze; however, anti-anxiety behaviors can be induced in these rodents (i.e. administration of anxiolytics), which can be strongly correlated to more time spent in the light, exposed arms of the maze.

Elevated Plus Maze

The open field test is used to evaluate fear in rodents. Subjects are placed in the center of a box with a defined “center” region, and are free to explore the box for a set duration. During the open field test, rodents exhibit a behavior known as “thigmotaxis,” in which they initially hug the walls of the area and later venture out into the center. This behavior is attenuated via anxiolytic drugs and is intensified in rodent strains with high anxiety.

Open Field Test

The Morris water maze, created by neuroscientist Richard G. Morris, is used to evaluate learning and memory in rodents. The maze consists of a pool of water with a single circular platform raised slightly above the water’s surface. To establish working memory, the rodents are placed in different quadrants of the pool and are allowed to freely swim and search for the platform. After the first day of training, the platform is submerged, and the next several days are dedicated to finding the submerged platform. Finally, the platform is removed, and the rodents’ memory is tested. More time spent in the platform’s quadrant correlates to stronger memory retention.

Morris Water Maze

As rodent models are ubiquitous among neuroscience and biomedical research, researchers have developed standardized assays to test specific behaviors, including but not limited to anxiety, stress, aggression, and cognition.

Pomona College

Rodents are the most widely used model organism in neuroscience and biomedical research. Rats and mice differ significantly in gene expression, social behaviors, and physiology, giving them unique advantages and disadvantages as the favorable model in any particular research. For example, mice were more commonly used due to their larger “genetic toolbox,” which includes transgenic and “knockout”/”knock-in” mice. However, adult rats typically weigh up to ten times more than adult mice. Their larger size makes surgery and other invasive procedures such as catheter insertion easier to perform, while mice are chosen for optogenetics experiments because light passes more easily through their smaller brains and can therefore reach deeper regions of the brain.

Rodentia (mouse, rat)

Ellenbroek, B., & Youn, J. (2016). Rodent models in neuroscience research: Is it a rat race? Disease Models & Mechanisms, 9(10), 1079–1087. https://doi.org/10.1242/dmm.026120

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